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What impact does ash accumulation in the radiation tubes have on the thermal effects inside the furnace?
Release time:
2022-03-31
What impact does ash accumulation in the radiation tubes have on the thermal effects inside the furnace?
How to improve the thermal efficiency during operation is generally believed to involve: grasping the patterns of flame shape changes; implementing precise and timely control to maintain the heat-transfer performance of the convection tubes; sealing gaps to minimize gas leakage; and adjusting the burner to ensure that the furnace operates with a dark flame, a fully developed flame, and a short flame. However, the impact of soot accumulation on the radiation tubes inside the furnace on heating efficiency has yet to receive sufficient attention. Factors affecting thermal efficiency include those within the furnace chamber itself. Radiation tube Accumulation of soot on the radiant tubes degrades their heat-transfer performance. To meet the requirements of the production process, it is necessary to raise the furnace chamber temperature, increase fuel consumption, and elevate the furnace wall temperature. As a result, the temperature at the furnace belly will rise, leading to increased heat loss from the furnace body. Once the furnace wall temperature rises, the air temperature inside the convection chamber will also increase, causing the flue-gas temperature to rise accordingly and increasing the heat loss through flue gases. From the above analysis, it can be seen that after soot accumulates on the radiant tubes, the heating furnace’s fuel consumption increases, as do heat losses and flue-gas heat losses. It is important to pay attention to the impact of soot accumulation on the thermal power of heating furnaces fueled by fuel oil or fuel oil mixed with fuel gas. During the combustion process within the furnace, when burning clean fuels such as light oil, there is virtually no ash formation. However, when burning heavy oils—especially residual oils and waste oils—the flue gases contain large amounts of oily ash, primarily composed of “scale” and “ash.” Scale refers to the non-combustible residues left behind after fuel combustion, mainly solid salts of equivalent metals; its quantity is comparable to the “ash content” determined in the fuel oil’s functional analysis. The ash component itself consists of particles remaining from the incomplete combustion of carbon—the combustible portion of the fuel oil—divided into “fine fly ash” and “coarse fly ash.” Although highly reactive, this ash merely adheres to the surfaces where heat transfer occurs.
A detailed introduction to the radiant tubes in heat treatment furnaces.
As far as heat treatment is concerned, the radiant tubes inside the furnace are crucial auxiliary equipment. Typically, the furnace... Radiation tube The core components are mainly available in three types: cage-frame type, vertically wound strip type, and resistance wire winding type. Meanwhile, the resistance wires are primarily made from nickel-chromium, iron-chromium-aluminum alloy materials, while the outer protective tubes are manufactured from seamless tubes, rolled welded tubes, and centrifugally cast tubes.
The outer diameter scale of the standard sleeve ranges from 80 to 280, with individual power ratings ranging from 2 kW to 40 kW and individual voltage ratings from 30 V to 220 V. The radiation tubes used inside the furnace are commonly employed in multi-purpose furnaces for bright quenching, normalizing, carburizing, and carbon-nitrogen co-diffusion processes on the side of the furnace. In addition, these tubes can also be used in various industrial heating applications such as rotary, casting, mesh belt, and joining processes. Typically, this equipment uses nickel-chromium or iron-chromium-aluminum alloys as its raw materials.
In comparison, the data for nickel-chromium alloys offer greater advantages in practical applications. Since they can be used within a temperature range of 500 to 800 degrees Celsius and exhibit a relatively stable, uniform, and homogeneous solid-solution structure, they possess superior mechanical properties, consistent electromechanical performance, and excellent processability. Compared with iron-chromium-aluminum electric heating alloys, nickel-chromium alloys also boast longer service lives and less damage. On the other hand, the data for chromium-aluminum electric heating alloys have a critical drawback: low ductility and high brittleness.
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